How do Diamonds Get Their Color?
Most natural diamonds are formed at extremely high temperatures and pressure. They are usually formed at the earth’s mantle at depths of 87 to 118 miles below. Minerals containing carbon provide the carbon source and takes 1 billion to over 3 billion years to form. They are brought to the Earth’s surface through volcanic eruptions by magma which cools into kimberlites and lamproites. Of course now diamonds can be produced synthetically using the HPHT method which simulates the conditions found in nature.
When in comes to colored diamonds many factors dictate the color as well as where on Earth they are found. According to GIA there are 27 different shades of colored diamonds, they also say that only 1 in 10,000 is a colored diamond.
Diamonds get their color from the infiltration of elements other than carbon. This also means that they have certain flaws and impurities.
Blue diamonds are rarely found in nature and their blue color is the result of boron atoms found in the face-centered cubic also called diamond lattice. Many blue diamonds are irradiated to create the blue and of course this greatly reduces the cost. Naturally blue diamonds are extremely pricey.
Boron is the element that creates the blue and is similar in size to carbon. When boron is present and the level of nitrogen is very low the diamond gets the blue color. Blue diamonds are mined in South Africa and Australia.
Green diamonds are extremely rare. It is estimated that less than 10 come to market each year. The green color is due to natural radiation from nearby rocks, although some green’s have trace amounts of nickel mixed into the carbon. The color is on the surface, so cutting and polishing a green must be done very carefully not to loose too much of the green color. Green diamonds are mined in Brazil, India, South Africa, Congo, Sierra Leone, and the Congo. However only a small amount come from Australia.
Yellow diamonds are very common, but the most vividly colored are mined in South Africa. They get the yellow color from inclusions of nitrogen, nitrogen atoms are similar enough to carbon that they easily take carbon’s place in the process. Interesting fact; if a yellow is not vivid enough it would be treated or “enhanced” with blue to pass the diamond as “colorless”.
Red absolutely the rarest of all colored diamonds, which in turn makes them the most expensive. Red diamonds are made purely from carbon, just like colorless diamonds. The red color is created by a deformation of it’s atomic structure, during their trip to the surface. Red’s are mostly found in Africa, Australia and Brazil.
Purple being the second most rare of colored diamonds. While there are several opinions as to why they are purple, it is believed that it is similar to red diamonds. Natural purples only account for 1% of the diamonds mined in Siberia. Most are only pale purple. The majority of them come from Australia.
Pink is thought to be due to changes in the electron structure, called plastic deformation during their trip to the surface. It is estimated that 90% come from Australia, but the are also found in Brazil, Tanzania and India.
Elements such as boron in the carbon structure can create a grey diamond. However, grey can also be a black diamond that is not thoroughly saturated. These are usually mined in India, Russia, Brazil, South Africa and Australia.
Traditionally black diamonds were mostly for industrial use. Black is not related to trace elements. Small inclusions of graphite and iron clusters create the black color. Colored diamonds are transparent, The numerous inclusions in a black diamond means it’s typically opaque. Because black diamonds have so many inclusions it fractures more easily when being cut, and many are not of gem quality. They are found in Africa, but mainly in Brazil.
Defects in the diamond lattice give brown diamonds their color, as the defects absorb light. Nitrogen is also present. “Champagne” and “Cognac” were used to better promote these diamonds. Brown diamonds are found in Australia, Africa and Siberia. Interested fact: a 2.93ct was found in Arkansas at Crater of Diamonds State Park.